The sleeping situation in Rivendell is far from ideal – not enough beds to go around and no one wants to share.

Arwen would rather sleep on the floor at the foot of the bed instead of sleeping, I don’t know, anywhere else.

Aragorn passes out next to Boromir’s bed; Boromir wakes up the next morning, flails around because Aragorn is blocking his way, and promptly falls back to sleep.